1. Technical Field
The present disclosure relates generally to electrical power management for hand held equipment, particularly managing electrical power supplied from several batteries.
2. Background Art
Tablet computers such as Apple Corporation's iPad®, Amazon's Kindle Fire and Barnes & Noble's Nook include a power management integrated circuit (“PMIC”) for converting electrical power at a battery's voltage to other required voltages. Usually, a tablet computer's PMIC provides electrical power at two (2) different voltages, i.e.:                1. a low voltage in the range of 1.8 v or lower for energizing operation of the tablet computer's microprocessor (“μP”) and perhaps other integrated circuits (“ICs”) included therein; and        2. a higher voltage in the range of 20-40 v for energizing operation of the tablet computer's display.        
As illustrated schematically in a block diagram FIG. 1A, a tablet computer frequently has battery system 22 that includes three (3) individual Li-Ion battery packs 24. In the illustration of FIG. 1A, a buck converter circuit 26 converts the voltage of direct current electrical power from the battery system 22, e.g. 4 v, to a lower voltage direct current electrical power, e.g. 1.8 v. Similarly, a boost converter circuit 28 converts the voltage of direct current electrical power from the battery system 22 to a higher voltage direct current electrical power, e.g. 24 or 36 v.
The configuration of the battery system 22 and the buck and boost converter circuits 26, 28 depicted in FIG. 1A uses a single battery voltage connected respectively to power inputs 32 of the buck and boost converter circuits 26, 28 for generating both 1.8 v and 36 v electrical power. The parallel arrangement of the battery packs 24 depicted in FIG. 1A is simple though it requires a high current for charging the battery packs 24 in parallel. However, the configuration depicted in FIG. 1A is not optimized for efficient power conversion by a PMIC. The depicted configuration favors efficient electrical power conversion by the buck converter circuit 26 but sacrifices electrical power conversion efficiency by the boost converter circuit 28.
As depicted in FIG. 1A, a tablet computer also usually includes a battery charger circuit 36 for supplying electrical power for recharging the battery packs 24. In conventional tablet computers the battery charger circuit 36 includes an input terminal 38 that receives electrical power from an external power source usually at approximately 5.0 v.
FIG. 1B illustrates in greater detail a power management circuit included in a typical hand held device 48 such as a tablet computer. Such a hand held device may include several individual buck converter circuits 26a, 26b, 26c that respectively supply electrical power at 1.0 v, 3.3 v and 2.5 v to a microprocessor 52, a WI-FI transceiver 54, and a RAM memory 56. The boost converter circuit 28 included in the hand held device 48 supplies electrical power to a display 58 at perhaps 24.0 v.
In addition to the battery charger circuit 36, the hand held device 48 also includes a detector circuit 62 that senses connection of an electrical power source such as an AD/DC adaptor 64 to the input terminal 38 of the hand held device 48. The detector circuit 62 responds to connecting a AD/DC adaptor 64 to the input terminal 38 by supplying a signal for closing a normally open switch 66 located between the battery charger circuit 36 and the battery system 22 so a recharging current flows to the battery packs 24.
U.S. Pat. No. 6,504,340 entitled “Hands-free Kit for Mobile Phones Using Solar Cell” that issued Jan. 7, 2003, on a patent application filed by Sea Sun Lee (“the '340 patent”) discloses, similar to the illustration of FIG. 1A, a configuration for recharging one or more batteries. During recharging, the batteries are connected in parallel with each other and with a solar cell that provides a low voltage source of charging electrical power. When supplying electrical power for energizing the operation of a disclosed “hands-free kit,” the rechargeable batteries become connected in series. While the batteries are being charged in parallel, the '340 patent's “hands-free kit” is inoperable.
Published United States Patent Application No. 2012/0293128 entitled “Battery Pack” filed by Bongyoung Kim and Kiho Shin that was published Nov. 22, 2012, similarly discloses connecting a plurality of batteries:                1. in parallel during high-efficiency charging that reduces overall charging time; and        2. in series when providing high-output voltage for energizing operation of a hand held electronic device such as a cellular phone, a notebook computer, a camcorder, or a personal digital assistant (PDA).        